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El efecto aparente de NAC en la mutasa del chorismato refleja la transición electrostática al estado de
Marek Strajbl1, Avital Shurki, Mitsunori Kato
1Department of Chemistry, University of Southern California, Los Angeles, California 90098-1062, USA.
Journal of the American Chemical Society
|August 21, 2003
Resumen
La chorismato mutasa (CM) utiliza principalmente la estabilización del estado de transición electrostática (TSS) para la catálisis, no la tensión estérica o la conformación de ataque cercano (NAC). Este TSS electrostático explica el poder catalítico de la enzima e influye en las distancias de los reactivos.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Enzimología Enzimología.
- Química computacional es la química computacional.
Sus antecedentes:
- La chorismato mutasa (CM) es una enzima clave con una actividad catalítica significativa.
- El mecanismo preciso que subyace a la potencia catalítica de CM, específicamente los roles de la estabilización del estado de transición electrostática (TSS), la tensión estérica y la conformación de ataque cercano (NAC), sigue siendo incompletamente entendido.
Objetivo del estudio:
- Para analizar cuantitativamente el mecanismo catalítico de la corismato mutasa (CM).
- Para determinar si el CM utiliza la estabilización del estado de transición electrostática (TSS), la tensión estérica o la conformación de ataque cercano (NAC) como su estrategia catalítica primaria.
- Para aclarar el origen de la potencia catalítica de CM.
Principales métodos:
- Se empleó el método de enlace de valencia empírica (EVB, por sus siglas en inglés) para reproducir el efecto catalítico general.
- Cálculo de las energías libres de unión tanto para el estado fundamental como para el estado de transición.
- Evaluación de la contribución electrostática a la reducción de la energía de activación.
Principales resultados:
- El método de enlace de valencia empírico (EVB) reprodujo con éxito el efecto catalítico de la chorismato mutasa (CM).
- El análisis demostró que la CM funciona a través de la estabilización del estado de transición electrostática (TSS), respaldada por cálculos vinculantes de energía libre.
- El efecto observado de conformación de ataque cercano (NAC) se identificó como una consecuencia, no una causa, del TSS.
Conclusiones:
- El mecanismo catalítico primario de la chorismato mutasa (CM) es la estabilización del estado de transición electrostática (TSS).
- Los efectos electrostáticos son la fuerza impulsora detrás de la reducción de la energía de activación observada en la catálisis de CM.
- Distribuciones de carga similares entre los estados de transición y reactivo dan lugar a TSS, lo que lleva a una reducción de la distancia interatómica en el estado reactivo.
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